License

curl and libcurl are distributed under an Open Source license known as a MIT license derivative. It is short, simple and easy to grasp. It follows here in full:

COPYRIGHT AND PERMISSION NOTICE

Copyright © 1996 - 2026, Daniel Stenberg, <daniel@haxx.se>, and many
contributors, see the THANKS file.

All rights reserved.

Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
OF THIRD PARTY RIGHTS. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

Except as contained in this notice, the name of a copyright holder
shall not be used in advertising or otherwise to promote the sale, use
or other dealings in this Software without prior written authorization
of the copyright holder.

This is legalese that says you are allowed to change the code, redistribute the code, redistribute binaries built from the code and build proprietary code with it, without anyone requiring you to give any changes back to the project—but you may not claim that you wrote it.

Early on in the project we iterated over a few different other licenses before we settled on this. We started out GPL, then tried MPL and landed on this MIT derivative. We do not intend to ever change the license again.